project on acetic acid

7/29/2019 project on acetic acid

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A I MMeasuring the Amount of Acetic

Acid

InVinegar

by Titration with

anIndicator Solution


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This is to certify that VINI

SHUKLA ofclass XII A1 has

completed thchemistryproject

entitled

DETERMINATION OF AMOUNT OF

ACETIC ACID IN VINEGAR

himself and under my guidance. The

progress of the project has been

continuously reported and has been in my

knowledge consistently.

Mrs.MAMTA SAINI(CHEMISTRY)

ST MARYS CONVENT SENOIR


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SECONDARY SCHOOL


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It gives me great pleasure to express my

gratitude

towards our chemistry teacher Mrs. ADITI

KAPOOR for her guidance, support

and encouragement throughout the

duration of the project. Without her

motivation and help the successful

completion of this project would not have

been possible.

VINI SHUKLA

XII

A1


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In de x1 Certificate

2 Acknowledgement

3 Aim

4 Objective

5 Introduction

6 Materials and Equipment

7 Theory

8 Experimental Procedure

Experiment 1

Experiment2

Experiment3

9 Result

10

Precautions

11


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Bibliography


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O b je c t iv

eThe goal of thisproject

is to determine the amount of Acetic

Acid in different types ofvinegar

using titration with a

coloured pH indicator to

determine the endpoint.


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Int r o duc t io nVinegar is a solution made from the fermentation ofethanol (CH

3CH

2OH), which in turn was previously

fermented from sugar. The fermentation of ethanolresults in the production of acetic acid (CH3COOH). Thereare many different types of vinegar, each starting from adifferent original sugar source (e.g., rice, wine, malt,etc.). The amount of acetic acid in vinegar can vary,typically between 4 to 6% for table vinegar, but up tothree times higher (18%) for pickling vinegar.

In this project, we will determine the amount of acid indifferent vinegars using titration, a common technique inchemistry. Titration is a way to measure the unknownamount of a chemical in a solution (the titrant) by addinga measured amount of a chemical with a knownconcentration (the titrating solution). The titratingsolution reacts with the titrant, and the endpoint of thereaction is monitored in some way. The concentration of

the titrant can now be calculated from theamount of titrating solution added, and the ratio of thetwo chemicals in the chemical equation for the reaction.

To measure the acidity of a vinegar solution, we canadd enough hydroxyl ions to balance out the addedhydrogen ions from the acid.

The hydroxyl ions will react with the hydrogen ions toproduce water. In order for a titration to work, we needthree things:

1. a titration solution (contains hydroxyl ions with aprecisely known concentration),

2. a method for delivering a precisely measured volume of ttitrating solution, and

3. a means of indicating when the endpoint has been reache

For the titrating solution, we'll use a dilute solution of


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sodium hydroxide (NaOH). Sodium hydroxide is astrong base, which means that it dissociates almostcompletely in water. So for every NaOH


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molecule that we add to the solution,we can expectto produce a hydroxyl ion.

To dispense an accurately measured volume of thetitrating solution, we will use a burette. A burette is a

long tube with a valve at the bottom and graduatedmarkings on the outside to measure the volumecontained in the burette. The burette is mounted on aring stand, directly above the titrant solution (as shownin the picture).

Solutions in the burette tend to creep up the sides of theglass at the surface of the liquid. This is due to thesurface tension of water. The surface of the liquid thus

forms a curve, called a meniscus. To measure the volumeof the liquid in the burette, always read from the bottomof the meniscus.

In this experiment, we will use an indicator solutioncalled phenolphthalein. Phenolphthalein is colourlesswhen the solution is acidic or neutral. When the solutionbecomes slightly basic, phenolphthalein turns pinkish,

and then light purple as the solution becomes morebasic. So when the vinegar solution starts to turn pink,we know that the titration is complete.


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M ate r ia ls an d

Eq u ipm en tTo do this experiment we will need the following materials andequipment:

Vinegar, three different types.

Distilled water

Small funnel

0.5% Phenolphthalein solution in alcohol (pH indicator solution)

0.1 M sodium hydroxide solution

125 mL Conical flask

25 or 50 mL burette

10 mL graduated cylinder

Ring stand

Burette clamp


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3

T h eo ryRequired amount of sodium hydroxide (NaOH) can

be calculated using the following formula:Molarity Molarmass Volume(cm

3

)W=

1000

Molar mass of NaOH = 40 g/mol

=0.5 40

500

1000

= 10g

The acetic acid content of a vinegar may bedetermined by titrating a vinegar sample with asolution of sodium hydroxide of known molarconcentration (molarity).

CH3COOH(aq) + NaOH(aq) --> CH3COONa(aq)+ H2O(l) (acid) + (base) --> (salt) +(water)

At the end point in the titration stoichiometry

between the both solution lies in a 1:1 ratio.

MCH COOH

VCH COOH 13 3

=M

NaOHV

NaOH1

Strength of acid in vinegar can be determined by thefollowing

formula:

Strength of aceticacid =

I nd i c a t o r : -

Phenolphthalein

E n d P o i nt : - Colourless to pink


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MCH COOH

60


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E x pe r imenta l

P r o c e dur ePerforming the Titration1. Pour 1.5 ml of vinegar in an Conical flask.

2. Add distilled water to dissolve the vinegar so thatthe volume of the solution becomes 20 mL.

3. Add 3 drops of 0.5% phenolphthalein solution.

4. Use the burette clamp to attach the burette to thering stand. The opening at the bottom of the buretteshould be just above the height of the Conical flaskwe use for the vinegar and phenolphthalein solution.

5. Use a funnel to fill the burette with a 0.1 Msolution of sodium hydroxide.

6. Note the starting level of the sodium hydroxidesolution in the burette. Put the vinegar solution to betitrated under the burette.

7. Slowly drip the solution of sodium hydroxide intothe vinegar solution. Swirl the flask gently to mixthe solution, while keeping the opening underneaththe burette.

8. At some point we will see a pink colour in thevinegar solution when the sodium hydroxide isadded, but the colour will quickly


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disappear as the solution is mixed. When thishappens, slow the burette to drop-by-drop addition.

9. When the vinegar solution turns pink and remains that coeven with mixing, the titration is complete. Close the tap

pinchvalve) of the burette.

10. Note the remaining level of the sodium hydroxidesolution in the burette. Remember to read from thebottom of the meniscus.

11. Subtract the initial level from the remaining levelto figure out how much titrating solution we haveused.

12. For each vinegar that we test, repeat the titrationat least three times.


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3

EX PERIM EN T 1

I. Take the h ouse h old vin e g ar in the conical flask

and do the titration with sodium hydroxide

(NaOH) as mentioned.

O B S E R VA T I O N S

S.no Volumeof

vinega

r

solutio

Burette Reading Volumeof

NaOH

solutio

n used

Initial

(in mL)

Final

(in

1. 20 0 27 27

2. 20 0 27 27

3. 20 0 27 27

Concordant volume = 27 m

C A L C U L A T I O N S

We know that,

MCH COOH

VCH COOH = MNaOHVNaOH

3

MCH

3COOH

MCH

3COOH

3

= M

NaOHV

NaOH

VCH COOH

= 0.5 27

20

= 0.675 mol/L

Strength of acetic acid= 0.675 60

=40.5 g/L


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33

EX PERIM EN T 2

I. Take the w ine vin e g ar in the conical flask and do the

titration with sodium hydroxide (NaOH) as

mentioned.


S.no Volumeof

vinega

r

solutio


NaOH

solutio

n used

Initial

(in mL)

Final

(in

1. 20 0 48 48

2. 20 0 48 48

3. 20 0 48 48

Concordant volume = 48 m


We know that,

MCH COOH


3

MCH

3COOH

MCH

3COOH

3

= M

NaOHV

NaOH

VCH COOH

= 0.5 48

20

= 1.2 mol/L

Strength of acetic acid=1.2 60

=72 g/L


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33

EX PERIM EN T 3

I. Take the fr u i t( P e r simm o n) vin e g ar in the conical

flask and do the titration with sodium hydroxide

(NaOH) as mentioned.


S.no Volumeof

vinega

r

solutio


NaOH

solutio

n used

Initial

(in mL)

Final

(in

1. 20 0 32 32

2. 20 0 32 32

3. 20 0 32 32

Concordant volume = 3 2 m


We know that,

MCH COOH


3

MCH

3COOH

MCH

3COOH

3

= M

NaOHV

NaOH

VCH COOH

= 0.5 32

20

= 0.8 mol/L

Strength of acetic acid= 0.8 60

=48 g/L


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Strenth

ofDifferent

Vinegars

R e su l tStrength of acetic acid in household vinegar = 40.5 g/L.

Strength of acetic acid in wine vinegar = 72 g/L.

Strength of acetic acid in fruit vinegar = 48 g/L.

Graphically plotting various vinegar

samples in accordance with the amount of

acetic acid present in them we present astunning find:

80

70

60

50

40

30

20

10

0

Household Vinegar Wine Fruit Vinegar

Order of amount of acetic acid in differensamples

of vinegar is:

Wine > Fruitvinegar> Householdvinegar


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P r e c a u t ion s Transference of measured vinegar into a

measuring flask should be done very carefully.

Measuring must be performed carefully.

Look at the meniscus of solution at eye level to

avoid parallax.

Look at the lower meniscus in the light colouredsolution and upper meniscus in the dark coloured

solution because of visibility.

Do not forget to add distilled water to the vinegar.


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project on acetic acid